The present invention generally relates to data storage apparatus and particularly relates to a head suspensions for disk-based data storage apparatus.
Conventional disk-based data storage apparatus comprises a rotatable data storage disk and a head suspension supporting a read/write head for generally radial movement across the surface of the disk. In operation, the head xe2x80x9cfliesxe2x80x9d over the rotating disk spaced from the surface of the disk by an air gap. The thickness of the gap is usually referred to as the xe2x80x9cflying heightxe2x80x9d of the head. Continuing advances in digital data recording onto disk are achieving increasing data recording densities. However, increased data recording densities demand corresponding reductions in spacing between the head and disk. The reduced flying height of the head, in turn, demands increased stability in the head-disk spacing. It would be desirable therefore to provide a relatively fast and highly sensitive sensor system for measuring the spacing between disk and the head.
In accordance with the present invention, there is now provided a head suspension for maintaining a gap between a read-write head and a data storage disk, the head suspension comprising: a heater for heating gas in the gap; and a sensor for generating an output indicative of the thickness of the gap, the sensor generating the output in dependence on thermal conductance across the gap.
Heat from the heater is transferred through the gap from the sensor to the disk by thermal conduction. The disk acts as a heat sink dissipating the heat transferred. If the thickness of the air gap decreases, conduction of heat from the sensor to the disk increases. The temperature of the heater therefore decreases. The temperature decrease at the heater, and therefore the corresponding decrease in gap thickness, is detected by the sensor. Conversely, if the thickness of the air gap increases, conduction of heat from the sensor to the disk decreases. The temperature of the heater therefore increases. The temperature increase at the heater, and therefore the corresponding increase in gap thickness, is detected by the sensor. The aforementioned temperature changes can be easily detected electrically, by monitoring, for example, current flow through a thermally-sensitive resistance. A similar technique is employed in the field of atomic force microscopy.
The present invention advantageously provides a relatively, low cost, fast and highly sensitive sensor system for measuring the spacing between the disk and the head in a disk storage apparatus.
In the interests of simplicity, the heater is preferably integral to the sensor. In preferred embodiments of the present invention to be described shortly, the sensor comprises a bar of silicon. The heater may then conveniently comprise a narrowed portion of the bar. The narrowed portion may, in turn, comprise a doped region thereby enhancing the sensitivity of the sensor. In the embodiments of the present invention, the head suspension comprises an elongate body having a first silicon layer, a silicon oxide layer disposed on the first silicon layer and a second silicon layer disposed on the silicon oxide layer, wherein the bar is located in the second silicon layer. Preferably, one end of the bar terminates in the second silicon layer and the other end of the bar terminates in an electrical contact isolated from second silicon layer. An aperture may be disposed between the narrowed portion and the silicon oxide layer to improve thermal isolation of the narrowed region. The head suspension may include an integral read-write head.
The present invention extends to control apparatus for controlling the thickness of a gap between a read-write head and a data storage disk, the control apparatus comprising: a head suspension as hereinbefore described; a comparator for generating an error signal indicative of any difference between the output from the sensor and a desired gap thickness; and an actuator for moving the head suspension relative to the disk to vary the thickness of the gap in dependence on the error signal.
The present invention also extends to disk storage apparatus comprising: a data storage disk; a read-write head; and control apparatus as hereinbefore described, for controlling the thickness of a gap between the head and the disk.
Viewing the present invention from another aspect, there is now provided a method for maintaining a gap between a read-write head and a data storage disk, the method comprising: supporting the read-write head via a head suspension; heating gas in the gap via a heater provided on the head suspension; and, generating an output indicative of the thickness of the gap in dependence on thermal conductance across the gap.
Viewing the present invention from yet another aspect, there is now provided a method for controlling the thickness of a gap between a read-write head and a data storage disk, the method comprising: supporting the read-write head via a head suspension; heating gas in the gap via a heater provided on the head suspension; generating an output indicative of the thickness of the gap in dependence on thermal conductance across the gap; generating an error signal indicative of any difference between the output from the sensor and a desired gap thickness; and, moving the head suspension relative to the disk to vary the thickness of the gap in dependence on the error signal